ISL problem! :S

[Squishy 0]

ey allIm new to this forum and signed up because i've been having this problem..Im not a noob in FS games, i know how it works and can usually land any plane on any airfield.Usually i land a jet using ILS frequency and approach autopilot. All goes well, i fly it manually to correct course, wait for the localizer to pop in..turn on APP etc..But now my problem, 1/4 times whenever i turn on the APP, the autopilot turns around, crashes the plane, or flies to another airfield. Now i did not fill in the wrong radio NAV1 frequency nor the wrong course(i checked 10x)..Two example:-Sometimes, when i set the NAV 1 to e.g. 190.50mhz (the correct one), the AP will just turn around to another airfield and with a totally different frequency (i checked all runways)-the autopilot will just turn around when i turn on APP (to e.g. HDG 103) even when the runway is straight ahead, im connected to that ILS frequency, and im flying HDG 280I can't figure it out..it must be some sort of bug in FS2004?thanks!

[enyap 0]

Maybe you've got the NAV/GPS switch still on GPS?John

[Squishy 0]

No, it's on NAV, i never touched it.edit: i'll make a short vid + a screenie of FSnavigator, brb!

[Jim Robinson 122]

Does it happen on an ILS that's worked OK in the past? Sounds like it's trying to fly the backcourse.Jim

[Squishy 0]

Yes i've had the problem 1x on an airfield that worked OK before.BC is off btw! But it's not always that it turns around, it may also take another localizer even though it's on a totally different ILS frequency :SHere's a picture (attached) of FSnavigator and a video of the problem:Video:http://wpxldk.googlepages.com/fsproblem.avi

[Jim Robinson 122]

That is a backcourse ILS, you can tell because the arrowhead on the ILS feather points out instead of in. To fly that one you'll need to get lined up and press your backcourse button. There won't be any glideslope, you'll have to use the VASI if there is one. If you just use your NAV or APP button, the autopilot is trying to fly the ILS for the opposite runway (10 in this case), that's why it tries to make a 180° turn.Jim

[Squishy 0]

Yes, i noticed that it's the wrong way around.But why?? according to my GPS and according to my FSnavigator the runway has a localizer from BOTH directions, and both have a different course! The one on the other side says 103. Why does it show the backcourse localizer when it says there's a localizer for both directions?

[scoob 18]

Squishy:from the charts only LOC landing on rwy 10. visual only for 28.see these charts -http://www.slv.dk/Dokumenter/dscgi/ds.py/View/Collection-398--

[RFields5421 1]

Microsoft made every localizer in FS with a backcourse active as the default. This causes aircraft to capture the backcourse and not the ILS on some runways where the localizer on both ends has the same frequency. We have to open airports with AFCAD in FS2004 and turn the backcourse off to make them reliable.That's not your issue here.First - BGSF does not have an ILS, in FS or the real world - it only has a localizer with a DME - no glidepath.The only reason you see "two" localizers on both ends is because you have Back Course ILS selected to display in the Options -> Settings -> Map configuration of FSNav.That's pretty much useless in FS because all localizers have back course enabled by default. It would be a great option if FS had only the real world localizers with Back Course step up correctly.Clicking the APPR mode of your autopilot without a glide slope can cause unpredictable behavior though normally it should just fly you over the runway.The reason your aircraft tries to turn away is because when you click the APPR button, you are telling the autopilot to fly the front course - at heading 103 degrees.

[Squishy 0]

Ah, so i guess that's it.I'll try turning the option off..weird it's turned on by default though:S!So just to be sure, whenever you use a backcourse, there's no glide slope? never?edit: ah i get it..you cant just turn it around like you can with a localizer..?thanks again;]

[Jim Robinson 122]

Not 100% certain, but I think you can fly a backcourse for the opposite runway on any ILS. If you look closely at the GPS and also the MS flight map, you'll only see an ILS feather for rwy 10 in this case, or at least that's all I'm seeing in my sim. It does however appear that the ILS transmitter (for rwy 10) is located on the threshold end of rwy28, which is I think different than what you normally see in the sim. FSnav generally always shows the backcourse feather for any ILS I believe.I suppose in the beginning, a real world airport would install an ILS for a particular runway, probably because it had the best obstacle free approach, or maybe the prevailing wind favored that runway most of the time. Soon pilots likely found that they could make use of the ILS from the opposite direction as well if they could somehow manage to fly the needle backwards. Next, avionics manufacturers decided that they could install a switch that reversed the needle movement on the VOR head, and labeled the switch "backcourse", so now the pilot could just press the backcourse button and fly the needle normally. Later, they slaved the autopilot to the VOR indicator and apparently it just does what the needle tells it to do, so if the backcourse switch is enabled, it flies the backcourse. If not, it makes a 180° turn and tries to fly the normal ILS for the opposite runway. I would imagine the To/From flag comes into play here as well.I have absolutely no idea if that's how it all came about, but that's the scenario that plays out in my mind anyway. :)Jim

[RFields5421 1]

It does however appear that the ILS transmitter (for rwy 10) is located on the threshold end of rwy28, which is I think different than what you normally see in the sim. FSnav generally always shows the backcourse feather for any ILS I believe.Normally a localizer antenna will be placed at the END of the landing runway - so having the antenna for Rwy 10 at the Rwy 28 threshold area is correct for an ILS. BGSF has a separate visual scenery object of a localizer antenna located near the east edge of the airport polygon. FS does a real good job of matching the location of such visual Common Library Objects with the position of the Navaid they represent.You want the localizer antenna to be at that end because you don't want the danged needle swinging 180 degrees as you cross the threshold for landing.But understand - that is the localizer - which is only one part of what is required for an ILS. It only provides lateral guidance so only needs to be lined up with the runway - or course because a LOT of them in the real world and FS do not line up with the runway.The other part of an ILS is the Glide Path or Glide Slope. These are often located near the landing end of the runway - about 900 feet from the threshold, but offset is the side of the runway by about 200-250 feet. In FS it's usually a 2x4x2 red and white panel shack with a 43 foot tall tower and the three transmitter horns for the three GP signals. It can be located differently - it's always how the transmitter horns are angled in the real world.I would strongly recommend you take a look at Juneau Alaska and landing on Rwy 08.First you will see the localizer is located about a mile short of the runway and does not line up with the runway.That is correct - that airport cannot have straight in ILS due to terrain issues. The localizer helps the pilot fly between the hills and make a 15 degree turn a mile from the end of the runway to land.

[RFields5421 1]

Looking at the approach plates - I would guess, and it's a pure guess - that the reason there is not an ILS at BGSF is there is not sufficient terrain clearnance for a missed approach when very low in very poor visibility.Also the runway slopes uphill when landing on Rwy 10 by 65 feet in elevation - flying almost blind into a rising runway is not a good ILS setup. "1.51% upslope on first 900M RWY 10. Upslope causes illusion of short runway"

[Jim Robinson 122]

Interesting Reggie, thanks for the insight. Especially that about MS setting all backcourses active. I didn't know that. Didn't know you could turn off backcourses in FSNav either. Yeah, I incorrectly reffered to a localizer as an ILS, and of course it's not an Instrument Landing System without the glideslope too.I've flown PAJN a number of times; CYLW (Kelowna, BC) is another like that, CYKA (Kamloops, BC) to a lesser degree, and CYCG (Castlegar, BC)... Well, I don't really know what they had in mind there.It looks like the localizer beam might get you into the canyon and possibly on a very close in downwind leg for rwy 33, but you'd better be flying a Skyhawk or a Cub if you're going to make base and final. Maybe it's not like that in TRW, but I know it's mountainous country, as I live about 60nm from there (straight line distance). Possibly the plan is to fly the localizer into the canyon and then shift to the left for a lndg on rwy 15. I'm guessing wind would be more favorable for the latter most times.Take a look at CYCG if you haven't already, naybe you can make some sense of it. Stop by 65S for a cup of coffee (or a beer) on your way back :) .Jim

[scott967 62]

In the US, at least, the older ILS systems use localizers having v-ring antenna arrays. These antennas provide a usable backcourse. The more modern installations utilize (mostly) log-periodic dipole antenna arrays. This type of antenna does not provide significant radiation on the backside.There are 40 ILS frequencies. In the US, FAA policy is to use same frequency when ILS's are sited at each runway end. There is required to be a interlock in the tower cab which permits radiation of only one system at any time.If you look at the geometry of an ILS antenna installation, you can see that a localizer can provide some guidance in the backcourse direction, but by virtue of being in front of the approach end of the runway, it isn't going to be accurate all the way down to 200 ft above threshold, like a normal localizer would. But the glideslope antenna, being at the far end of the approach runway in this situation, is going to be of limited or no value, even if you could design one with a good radiation pattern on the backside.FS apparently makes no attempt to determine if a localizer has backcourse capability or not IRL. Also, it does not model the interlock of same-freq ILS systems serving opposite runway ends.scott s..